1. Field of the Invention
The present invention relates to a method of evaluating an optical beam source of an exposure device, a method of designing illumination shape of an exposure device, and a software for optimizing illumination shape of an exposure device, and is particularly used in an exposure process in manufacturing a semiconductor device and the like.
2. Description of the Related Art
In an exposure process in manufacturing a semiconductor device and the like, an illumination shape for forming a desired resist pattern is designed by using photomasks having a plurality of different patterns (for example, line-and-space pattern, isolated line pattern, hole pattern). In the designing, the exposure optical beam source is divided into small grids to form a plurality of unit optical beam sources (or spot optical beam sources). In this case, an evaluation of the unit optical beam sources is made by using, as an index, an intensity of an image formed by each of the unit optical beam sources, a contrast of the image, NILS (normalized image log-slope), or the like.
However, satisfactory measures are not taken into consideration by these indices alone, if the optical beam source is not formed exactly as designed, for example, if there is an error in an illumination aperture.